# Test Bank Ch1

Test Bank—Chapter One (Data Representation) Multiple Choice
Questions
1. Which of the following Boolean operations produces the output 1 for the fewest number of input patterns?

2. Which of the following best describes the NOR operation?
3. Which of the following bit patterns cannot be expressed in hexadecimal notation?
4. Which of the following is the binary representation of 4 5/8?

A. 100. 11
B. 10. 11
C. 110. 101
D. 100. 101

5. Which of the following bit patterns represents the value 5 in two’s complement notation?

A. 00011010
B. 11111011
C. 00000101
D. 11111011

6. Which of the following bit patterns represents the value -5 in two’s complement notation?

A. 00011010
B. 11111011
C. 00000101
D. 11111011

7. In which of the following addition problems (using two’s complement notation) does an overflow error occur?

A. 0011
B. 0100
C. 1100 + 1010 + 0100 + 1100

8. Which of the following representations in two’s complement notation represents the largest value?

A. 00000010
B. 11111111
C. 00000001
D. 11111110

9. Which of the following bit patterns (represented in hexadecimal notation) represents a negative number in two’s complement notation?

A. 7F
B. 55
C. A6
D. 08

10. What value is represented by the bit pattern 01011100 when interpreted using floating-point format in which the most significant bit is the sign bit, the next three bits represent the exponent field in excess notation, and the last four bits represent the mantissa?

A. -1 1/2
B. 1 1/2
C. -3/8
D. 3/8

11. Which of the following values cannot be stored accurately using a floating-point format in which the most significant bit is the sign bit, the next three bits represent the exponent field in excess notation, and the last four bits represent the mantissa?

A. 2 1/2
B. 3/16
C. 7
D. 6 1/4

12. Which of the following bit-patterns represents the smallest value using the floating-point format in which the most significant bit is the sign bit, the next three bits represent the exponent field in excess notation, and the last four bits represent the mantissa?

A. 01001000
B. 1011000
C. 00101000
D. 01111000

13. Which of the following data storage systems provides the most efficient random access to individual data items?

A. Main memory
B. Magnetic disk
C. Optical C
D. and DVDs

14. Which of the following storage systems is best suited for storing and retrieving long strings of data that are processed in their sequential order?

A. Main memory
B. Magnetic disk
C. Optical C
D and DVDs

15. Which of the following mass storage system does not require physical motion?

A. Magnetic tape
B. Magnetic disk
C. DVDs
D. Flash drives

16. Assuming that each of the following bit patterns originally had even parity, which one contains an error?

A. 10110100
B. 11000011
C. 00011000
D. 10001001

17. How many errors per pattern could be corrected when using an error-correcting code in which any two code patterns differ by a Hamming distance of 8?

A. 3
B. 4
C. 5
D. 6

18. Which of the following is a possible LZW compression of the message “xyz xyz xyz”?

A. 1234
B. 1234545
C. 232
D. 12

19. How many different symbols can be encoded using Unicode?

A. 256
B. 4,096
C. 65,536
D. 1,046,476

20. Which of the following systems is least efficient when encoding numeric values?

A. Two’s complement notation
B. Excess notation
C. ASCII
D. Floating-point notation

21. Which of the following is a means of encoding music?

A. ASCII
B. MIDI
C. JPEG
D. GIF

Questions
1. A computer’s main memory consists of numerous memory cells, each of which contains ________ bits. Each memory cell is identified by a numeric value called the cell’s _________. ANSWER: eight, address
2. Represent the bit pattern 1011010010011111 in hexadecimal notation. ________ ANSWER: B49F
3. A7DF is the hexadecimal representation for what bit pattern? ____________ ANSWER: 1010 0111 1101 1111
4. How many different bit patterns can be formed if each must consist of exactly 6 bits? ____________ ANSWER: 64
5. Translate each of the following binary representations into its equivalent base ten representation.

A. 1100__________
B. 10. 011__________
C. 0. 01 __________
D. 10001__________

ANSWER: A. 12 B. 2 3/8 C. 1/4 D. 17
6. Rewrite each of the following values (represented in base ten notation) in binary notation.

A. 7__________
B. 23__________
C. 2 1/4 __________
D. 5/8__________

ANSWER: A. 111 B. 10111 C. 10. 01 D. 0. 101
7. If the patterns 101. 11 and 1. 011 represent values in binary notation, what is the binary representation of their sum? ____________
8. Using a two’s complement notation system in which each value is represented by a pattern of six bits, represent the value 3. ____________ ANSWER: 000011
9. Using a two’s complement notation system in which each value is represented by a pattern of six bits, represent the value -3. ____________ ANSWER: 111101
10. What is the largest positive integer that can be represented in a two’s complement system in which each value is represented by eight bits? ____________ ANSWER: 127 (represented by 01111111)
11. In a two’s complement system, what value is represented by the pattern 11111111111111001? _________ ANSWER: -7
12. When using two’s complement notation, what bit pattern represents the negation of 01101010? ____________ ANSWER: 10010110
13. What value is represented by each of the following patterns in excess notation?

A. 10000 ____
B. 0110 ____
C. 1011 ____

ANSWER: A. 0, B. -2, C.
14. Using an 8-bit floating-point format in which the most significant bit is the sign bit, the next three bits represent the exponent field in excess notation, and the last four bits represent the mantissa, write the bit pattern that represents the value 1 3/4. (Use normalized form. ) ____________ ANSWER: 01011110
15. What is the largest value that can be represented in a floating-point system in which each value is encoded by a byte whose most significant bit is the sign bit, the next three bits represent the exponent field in excess notation, and the last four bits represent the mantissa? ___________ ANSWER: 7 1/2 (represented as 01111111)
16. Which of the following addition problems cannot be solved accurately when using a floating-point system in which each value is encoded by a byte whose most significant bit is the sign bit, the next three bits represent the exponent field in excess notation, and the last four bits represent the mantissa? A. 2 1/2 + 1 3/8B. 3 1/2 + 4 1/2C. 7 + 3/4 ____________ ANSWER: A, B, and C
17. The following is an error-correcting code in which any two patterns differ by a Hamming distance of at least three. Symbol Representation

A 000000
B 001111
C 010011
D 011100
E 100110
F 101001
G 110101
H 111010

Decode each of the following patterns 010011 ________101010 ________011000 ________101101 _______ ANSWER: C, H, D, F
18. How many errors in a single code pattern could be corrected when using an error-correcting code in which each code pattern is a Hamming distance of at least seven from any other code pattern? ____________ ANSWER: 3
19. The following is a message that was originally encoded so that each pattern had odd parity. Circle the patterns in which an error has definitely occurred. 0110101 11110000 10010010 00000000 11111111 00001000 00111101 ______________________________________
ANSWER: Second, fourth, fifth, and sixth
20. Data compression techniques apply various principles to reduce the size of data. One, called _______________________, avoids repeating long strings of the same data item. Another, called _______________________, encodes the difference between consecutive blocks of data rather than encoding each block in its entirety. Still another, called _________________________, uses short bit patterns to encode frequently occurring items and longer patterns to encode less frequent items.
ANSWER: Run-length encoding, relative encoding, and frequency-dependent encoding.
Vocabulary (Matching)
Questions
The following is a list of terms from the chapter along with descriptive phrases that can be used to produce questions (depending on the topics covered in your course) in which the students are ask to match phrases and terms. An example would be a question of the form, “In the blank next to each phrase, write the term from the following list that is best described by the phrase. ” TermDescriptive Phrase bitBinary digit Boolean operationAND, OR, XOR, NOT addressA numeric value used to identify a memory cell exadecimal notationAn efficient way of representing bit patterns sectorA segment of a track in a mass storage system zoned-bit recordingA means of increasing the storage capacity of a magnetic disk system bufferA storage area used to hold data on a temporary basis, often as a step in transferring the data from one device to another ISOAn international organization for establishing standards. ANSIA major standardization organization within the United States ASCIIA system developed by the American Standards Institute for encoding text. lip-flopA digital circuit capable of holding a single digit two’s complement notationA means of encoding whole numbers floating-point notationA means of encoding numeric values that may involve fractions truncationAn error that may occur when using floating-point notation pixelA small part of an image GIFA means of compressing an image file by restricting the number of colors available
JPEGA means of compressing images by blurring the boundaries between different colors while maintaining all brightness information UnicodeA means of encoding text in which each symbol is represented by 16 bits LZWAn example of adaptive dictionary encoding MIDIA means of encoding music in terms of notes and instruments rather than actual audio Key fieldA part of a logical record in a file used to identify the record. VLSIA means of constructing complex circuitry in a very small space.
General Format Questions
1. Describe how a computer can produce an incorrect answer when performing numerical computations even though it has not malfunctioned.
ANSWER: Most students will probably refer to overflow and truncation errors.
2. Describe ho the concept of Hamming distance is used to produce an error-correcting code.
ANSWER: By designing a code in which each pattern has a Hamming distance of n from any other pattern, patterns with fewer than n/2 errors can be corrected by replacing them with the code pattern that is closest.

a. What is the output of the circuit below?
b. In general, how does the three-bit input pattern across the top of the diagram relate to the circuit’s output? ANSWER: a. 0 b.

3. The output is 0 if the input parity is odd; the output is 1 if the input parity is even.
4. If the input and output bit patterns in the circuit below are interpreted as binary representations of numeric values, what operation does the circuit perform?
ANSWER: The circuit subtracts one (except for the case of the input being 000).
5. Explain why such terms as kilobyte, megabyte, and gigabyte have acquired double meanings.
ANSWER: The prefixes kilo, mega, and giga are used traditionally to refer to units measured in powers of ten. However, due to the early misuse of the prefix kilo in reference to units of the size 1024, these prefixes are now often used to refer to units that are powers of two—especially when referring to the capacity of main memories.
6. Convert the following addition problem into two’s complement notation using four bits per value), perform the addition, convert the answer back into base ten notation, and explain the results. 6 + 3 ANSWER: In two’s complement notation the problem is to add 0110 and 0011. The sum is 1001 which translates to -7. This answer is incorrect due to overflow.
7. Under what condition is each of the following data compression techniques most effective?

a. Run-length encoding
b. Relative encoding

ANSWER: a. Compresses most when data consists of long strings of the same entry. b. Compresses most when each block of data differs little from the previous block.
8. What is frequency-dependent encoding?
ANSWER: Frequency-dependent encoding is an encoding system that uses short bit patterns to represent data items that occur most often and longer patterns to represent less frequently occurring items. The result is that entire blocks of data can be represented in less space than would be required if each data item were represented by the same size bit pattern.
9. Construct the entire two’s complement scale in which each value is represented by three bits.
ANSWER: 3 011 2 010 1 001 0 000 -1 111 -2 110 -3 101 -4 100
10. To what does the term “normalized form” refer in the context of floating-point notation? ANSWER: Normalized form refers to a standard for positioning the bit pattern within the mantissa field. Many values can be represented in floating-point notation by different bit patterns, only one of which is in normalized form. Hence, restricting representations to normalized form assures that each value is represented by a unique pattern.
11. Explain why the final version of the dictionary need not be transmitted with a message encoded using LZW compression.
ANSWER: The dictionary can be constructed during decompression in the same way it was constructed during compression.
12. Among the Boolean operations AND, OR, EXCLUSIVE OR, and NOT, which is least like the others? Explain your answer.